Image inputting apparatus and image forming apparatus using four-line sensor

ABSTRACT

A four-line CCD sensor is structured by line sensors R, G, B in which color fillers are respectively disposed on surfaces of light receiving elements, and a line sensor BK at which no color filter is disposed. Amplitudes of signals which are outputted from the line sensors R, G, B at a time of reading a color document, and an amplitude of a signal which is outputted from the line sensor BK at a time of reading a monochrome document are adjusted so as to be substantially equal to one another. In a case in which a color document is read, outputs of the line sensors R, G, B are selectively provided, and in a case in which a monochrome document is read, output of the line sensor BK is selectively provided.

More than one reissue application has been filed for U.S. Pat. No.6,958,835. This continuation reissue application is a continuation ofapplication Ser. No. 11/976,452, filed Oct. 24, 2007, which in turn is areissue application of application Ser. No. 09/955,090, filed Sep. 19,2001, now U.S. Pat. No. 6,958,835.

BACKGROUND OF THE INVENTION

The present invention relates to an image inputting apparatus such as ascanner or the like which reads image information by scanning adocument, and to an image forming apparatus such as a digital copier orthe like which uses the image inputting apparatus.

Conventionally, there are generally two types of CCD line sensors whichare used in a reduction optical system: a CCD line sensor which isstructured by only a one-line line sensor, and a CCD line sensor whichis structured by a three-line line sensor in which color filters of red(hereinafter denoted as R), green (hereinafter denoted as G), and blue(hereinafter denoted as B) are disposed on the surfaces of therespective line sensors.

The aforementioned one-line CCD line sensor is basically used forreading monochrome (white/black) documents. When a color document isread by using this CCD line sensor, a method is adopted in which, bysuccessively turning on three light sources having spectralcharacteristics of R, G, B which are three primary colors of light, theimage information of the color document is divided into colorinformation of R, G, B and read. Further, there is a method which uses alight source whose spectrum characteristic is white, and color filtersof R, G, B are disposed on the optical path from the light source to theline sensor, and by switching the color filters, the color informationwhich is incident on the line sensor is separated.

The aforementioned three-line CCD line sensor is basically used forreading color documents. For the light source in this case, a lightsource which has a spectral characteristic which sufficiently covers thevisible light region from oscillation wavelengths of 400 nm to 700 nm isused. The division of the color information of R, G, B is carried out bythe color filters which are disposed on the surfaces of the respectiveline sensors.

Further, when a monochrome document is read by using the three-line linesensor, there are cases in which one output among the three linesensors, generally, the line sensor output of G, is used in order toreliably read a vermilion impression, and there is a method in whichwhite/black information is generated by using all of the outputs of thethree line sensors.

When color information is read by a CCD sensor which is structured by aone-line sensor, as described above, a method of the switching lightsources or switching the color filters is used. Thus, there aredisadvantages in that the control of the light source relationships iscomplicated, and costs accompanying such control increase.

When single color information is read by using one line sensor output ofa CCD sensor which is structured by a three-line sensor, for example, ina case in which the line sensor having sensitivity of G is used, asdescribed above, information in vermilion can be read. However, thegreen color information and the white information on the document cannotbe distinguished from one another, and as a result, information of greencharacters or images or the like cannot be read. In the same way, in acase in which the line sensor having sensitivity of R is used, adrawback arises in that the red information cannot be read, and in acase in which the line sensor having sensitivity of B is used, adrawback arises in that the blue information cannot be read.

In a case in which white/black information is generated by using all ofthe outputs of the three line sensors, because the three line CCD sensoris arranged such that the three line sensors are disposed to bephysically separate from one another, the respective line sensors cannotread the information at the same area. Accordingly, in order to correctthe offset of the positions, it is necessary to effect correction inline units by using line buffers.

Further, at the time of reading, if the distances between the lines ofthe three line sensors are in a proportional relationship which is aninteger multiple of a one-line reading range in the subscanningdirection on the document, precise alignment can be achieved by theaforementioned line buffers. However, because the one-line reading rangein the subscanning direction varies in accordance with the readingmagnification, there is the problem that the above-describedproportional relationship is not established, and the alignment of colorinformation by the line buffers is poor. Moreover, in a case in which animage is rapidly changed from white to black or from black to white suchas a monochrome characters, the drawback that false colors such as redor blue are generated at the changing points arises.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an image inputtingapparatus and an image forming apparatus which can read colorinformation of a document, and can provide image data in whichpositional offset and false colors do not arise in a case in which amonochrome document is read.

In order to achieve the above-described object, in the presentinvention, the image inputting apparatus is formed by using a four-lineCCD sensor in which a one-line sensor, which is for reading a monochromedocument, and a three-line sensor, which is for reading a color documentand in which color filters of R, G, B are respectively disposed on thelight receiving surfaces, are disposed in the same device.

Because the four-line CCD sensor is formed by line sensors at whichcolor filters are disposed and a line sensor at which no color filter isdisposed, the sensitivities which are the photoelectric convertingefficiencies of the respective line sensors greatly differ.

The present invention is for correcting the aforementioned differencesin sensitivities by signal processing.

In a case in which a color document is read, by using the three linesensors at which color filters are disposed, the transferring speed ofthe image signal is set to be lower than that at the time when amonochrome document is read by one line sensor at which no color filteris disposed, and the light accumulating time of one line is made long.

Further, in a case in which a color document is read, by using the threeline sensors at which color filters are disposed, the illuminance of thedocument surface is set to be higher than that in a case in which amonochrome document is read by one line sensor at which no color filteris disposed.

The image inputting apparatus has two light sources as means forcontrolling the aforementioned illuminance of the document surface.Reading operation is carried out by turning on the two light sources atthe time of reading a color document, or by turning on one of the twolight sources at the time of reading a monochrome document.

When a processing for optimizing the outputted analog signal from thefour-line sensor to the input amplitude of the subsequent stageanalog/digital converter is carried out, the amplification factor of thegain amplifier which amplifies the output signal of a line sensor atwhich a color filter is disposed is set to be higher than theamplification factor of the gain amplifier which amplifies the outputsignal of the line sensor at which no color filter is disposed.

The photoelectric converting efficiency (sensitivity) of the line sensorat which no color filter is disposed is high as compared with those ofthe three line sensors at which the color filters of R, G, B arerespectively disposed. Thus, the line sensor can be driven at highspeed. Further, because the photoelectric converting efficiency of theline sensor at which no color filter is disposed is high, the outputsignal of the line sensor is divided into an even signal and an oddsignal which are outputted as parallel signals of two systems, and thelight accumulating time is shortened. Moreover, the even signal and theodd signal may be divided into two, and may be outputted as parallelsignals of four systems.

The setting as to whether a document is to be read as a color documentor as a monochrome document can be easily switched by a request from theuser. Further, whether a document is a color document or a monochromedocument can be detected by a document automatic detecting section, andthe above-described reading operation can be switched.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the schematic structure of an image inputting apparatususing a four-line CCD sensor;

FIG. 2 is a block diagram showing the structure of a control system ofthe image inputting apparatus;

FIG. 3A shows a general view of the four-line CCD sensor, and FIG. 3Bshows the structure of a light receiving surface;

FIG. 4 shows the schematic structure of the fourline CCD sensor;

FIG. 5 shows a spectral sensitivity characteristic of a line sensor BKin the four-line CCD sensor;

FIG. 6 shows a spectral sensitivity characteristics of line sensors R,G, B in the four-line CCD sensor;

FIG. 7 shows a spectral distribution characteristic of a xenon lightsource which is an example of a light source;

FIG. 8 shows a driving timing and an output signal waveform of a CCDsensor;

FIGS. 9A and 9B show reading timings per line sensor of the presentinvention;

FIG. 10 is a flowchart showing the operation of a first embodiment;

FIG. 11 is a flowchart showing the operation of a second embodiment;

FIGS. 12A to 12C show the structure and the operation of a thirdembodiment;

FIG. 13 is a flowchart showing the operation of the third embodiment;

FIGS. 14A and 14B show a processing circuit structure and a signalwaveform of an analog signal which is outputted from a CCD sensor;

FIGS. 15A and 15B show a basic circuit of a gain amplifier section;

FIGS. 16A and 16B show the schematic structure and an output signaltiming of a four-line CCD sensor in which a line sensor BK output ismade to be 2CH;

FIG. 17 shows a driving timing and an output waveform of the four-lineCCD sensor which is shown in FIG. 16;

FIGS. 18A and 18B show a schematic structure and an output signal timingof another four-line CCD sensor in which a line sensor BK output is madeto be 4CH;

FIGS. 19A and 19B show a schematic structure and an output signal timingof yet another four-line CCD sensor in which a line sensor BK output ismade to be 4CH;

FIG. 20 shows an outline of a copy apparatus which is structured by animage inputting apparatus and an image forming apparatus;

FIG. 21 shows an example of the structure of a control panel;

FIGS. 22A and 22B show copying operations in a copy apparatus which isstructured by an image inputting apparatus and an image formingapparatus;

FIGS. 23A and 23B are explanatory figures in a case in which a copyapparatus, which is structured by an image inputting apparatus and animage forming apparatus, is used as a network printer;

FIGS. 24A and 24B are explanatory figures in a case in which a copyapparatus, which is structured by an image inputting apparatus and animage forming apparatus, is used as a network scanner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the figures.

FIG. 1 shows the structure of an image inputting apparatus 1 relating tothe present invention using four-line CCD sensor. The image inputtingapparatus 1 is an apparatus which reads image information of a documentat a scan line interval which corresponds to the resolution.

A document D is placed face down on a document stand glass 10. Byclosing a cover 11 for document fixing which is provided so as to befreely openable and closable, the document D is pressed onto thedocument stand glass 10. The document D is irradiated by a light source12, and the reflected light from the document D is image-formed onto asensor surface of a photoelectric converting element 17 via mirrors 13,14, 15, and a collective lens 16. Due to a first carriage 1A, which isstructured by the light source 12 and the mirror 13, and a secondcarriage 1B, which is structured by the mirrors 14, 15, being moved fromthe left toward the right by a motor for carriage driving which is notshown, the document D is scanned by the irradiated light from the lightsource 12. Further, by setting the moving speed of the first carriage 1Ato be two times the moving speed of the second carriage 1B, the opticalpath length from the document D to the four-line CCD sensor 17 which isthe photoelectric converting element is controlled so as to be constant.

In this way, the image of the document D which is placed onto thedocument glass 10 is, by the four-line CCD sensor 17 and per scan line,converted into an analog electric signal which corresponds to the lightsignal strength of the reflected light, and is successively read.

FIG. 2 is block diagram showing the structure of the control system ofthe image inputting apparatus 1. The image inputting apparatus 1includes a scanner control section 40 and a control panel section 80.

The scanner control section 40 includes a CPU 100, a ROM 101, a RAM 102,a CCD driver 103, a scanner motor driver 104, an image correctingsection 105, an image processing section 106, a document automaticsensing section 107, and a light source control section 108 whichcontrols the light source 12. Moreover, the scanner control section 40includes a driver, which is not illustrated, which drives a movingmechanism such as a mechanism which moves the collective lens 16 to theposition which corresponds to the set magnification.

The CPU 100 controls the scanner control section 40 overall inaccordance with a control program including the present invention whichis stored in the ROM 101, and uses the RAM 102 for temporary storage ofdata. The CCD driver 103 drives the four-line CCD sensor 17, and thescanner motor driver 104 controls the rotation of the driving motorwhich moves the first and second carriages 1A and 1B and the like. Thedocument automatic sensing section 107 automatically senses whether adocument which is placed onto the document stand glass 10 is a colordocument or a monochrome document or single color document.

The image correcting section 105 includes an A/D converting circuitwhich converts an analog signal from the four-line CCD sensor 17 to adigital signal, and a shading correcting circuit and a gamma correctingcircuit for correcting dispersion of the four-line CCD sensor 17 orfluctuations of a threshold level with respect to the output signal fromthe four-line CCD sensor 17 which are caused by temperature changes atthe periphery or the like. Further, the image correcting section 105includes a line memory which once stores the corrected digital signalsfrom these correcting circuits. The image processing section 106 carriesout image processings such as trimming, masking, enlargement/reductionprocessings, resolution conversion, image compression/decompressionprocessings, and the like on the image data which is inputted from theimage correcting section 105.

The control panel section 80 includes a key pad 82, a panel CPU 83, anda liquid crystal display section 84. A screen for setting documentreading conditions or the like is displayed at the liquid crystaldisplay section 84. The panel CPU 83 receives data relating to thedocument reading conditions which is key-inputted by a user via the keypad 82, and transfers the key-inputted data to the scanner controlsection 40, and displays the key-inputted data at the liquid crystaldisplay section 84. The document reading conditions include theinformation of whether the document is to be read as a color document oras a monochrome document, and information on the resolution, and thelike.

FIG. 3A is a general view of the four-line CCD sensor 17, and FIG. 3B isan enlarged view of a light receiving section 17a. In the four-line CCDsensor 17, at the light receiving section 17a of the line sensors, foursensors which are a line sensor BK at which no color filter is disposed,a line sensor R at which a filter having red color sensitivity isdisposed, a line sensor B having blue color sensitivity, and a linesensor G at which a filter having a green color characteristic isdisposed, are provided so as to be aligned. In each of the line sensors,for example, photodiodes, which serve as light receiving elements, aredisposed at a pitch of 7μ.

At the four-line CCD sensor 17, the four line sensors are disposed so asto be aligned in this way. Thus, the position of each line sensor isphysically offset. Accordingly, there is the problem that the same scanline on the document D cannot be read simultaneously by the four linesensors. This problem is usual for CCD line sensors which are formed bya plurality of line sensors using a reducing optical system. Thepositional offset of the image information which is read is corrected bya line memory or the like in the image correcting section 105.

Next, the characterizing features of the four-line CCD sensor 17discussed above will be described.

FIG. 4 is a schematic structural view of the four-line CCD sensor 17,FIG. 5 shows a spectral sensitivity characteristic of the line sensor BKforming the four-line CCD sensor 17, and FIG. 6 shows the spectralsensitivity characteristics of the line sensors R, G, B.

As described above, the four-line CCD sensor 17 is formed by the linesensor BK, in which no color filter is disposed at the light receivingsurface portion of the line sensor, and line sensors R, G, B at whichcolor filters are disposed. As will be described later, when light isilluminated onto the line sensor, charges accumulate in accordance withthe illuminated light amount and the illumination time at the lightreceiving elements which are disposed in a straight line. In response toan SH signal, the accumulated charges are supplied to an analog shiftregister via a shift gate. Synchronously with transfer clocks CLK1, 2,the analog shift register serially outputs the charges supplied from therespective light receiving elements.

When light is illuminated uniformly onto the line sensors, as shown inFIGS. 5 and 6, the line sensor R or the line sensor G or the line sensorB only has sensitivity with respect to wavelengths in a specific region,whereas the line sensor BK has sensitivity from a wavelength range ofless than 400 nm to a portion exceeding 1000 nm. Accordingly, the analogsignal amplitude which is outputted from the line sensor BK is greaterthan the analog signal amplitudes outputted from the line sensors R, G,B. For reference, an example of the spectral distribution of a Xenonlight source is shown in FIG. 7.

Next, operation of the CCD line sensor will be described.

When the document D is, for example, an A4 size document, the document Dhas a surface area of 297 mm in the longitudinal direction and 210 nm inthe short-side direction. When the document is read at a resolution of600 dpi with the longitudinal direction being the main scanningdirection and the short-side direction being the subscanning direction,the required number of effective pixels of the photodiode array of thefour-line CCD sensor 17 is 7016 pixels at the minimum (4677 pixels atthe time of 400 dpi). Generally, there are sensors of 7500 pixels (5000pixels at the time of 400 dpi). Further, as shown in FIG. 8, the CCDline sensor has, at a portion of the photodiode array, a light shieldingpixel portion which shields light and is formed of aluminum or the like,and dummy pixels, and an empty feed portion, so that light is notincident onto the stages before the 7500 pixels which are the effectivepixels. Accordingly, a transfer CLK number which exceeds the 7500 pixelsis needed in order to output to the exterior all of the chargesaccumulated in the CCD line sensor. Here, if the total of the lightshielding pixel portion, the empty feed portion, and the dummy pixelportion, which are outside of the effective pixel region, is a transferCLK number of 500, a time corresponding to 8000 transfer CLK is requiredin order to output to the exterior of the CCD line sensor all of thecharges which have been accumulated in one line of the CCD line sensor.This time is the light accumulating time for one line (tINT).

Further, as the characterizing feature of the output signal of the CCDline sensor, a signal is outputted in the minus direction by using, as areference, a voltage level which is offset by a given constant valuewith respect to an electrical reference level (GND). This voltage levelwhich is a reference is called the signal output DC voltage (offsetlevel; Vos).

Next, the internal operation of the four-line CCD sensor 17 will bedescribed.

The light energy, which is illuminated onto the line sensor at the timewhen the SH signal within the one line light accumulating time (tINT) is“L” level, is accumulated as charges in the photodiodes. When the SHsignal is “H” level, the accumulated charges pass through the shift gatewhich is adjacent to the photodiodes, and are transferred to the furtheradjacent analog shift register.

When this transfer operation is completed, the SH signal is made to be“L” level, and the shift gate is operated. The charge accumulatingoperation at the photodiodes is again started so that the charges do notleak to the exterior of the photodiodes.

The charges which are transferred to the analog shift register aretransferred, in pixel units, to the exterior at the transfer CLK period.Due to this operation, the SH signal is applied such that the transferCLK is stopped during the time that the charges which pass through theshift gate from the photodiodes move to the analog shift register.

The transfer CLK is always inputted, and even in cases in which thetransfer CLK matches the SH signal at the interior of the CCD linesensor and the transfer CLK is stopped, the charge transfer operation atthe interior is the same. Further, due to the CCD line sensor, there arecases in which the polarities of the above-described SH signal and thetransfer CLK differ from FIG. 8, but the internal operation of thesensor is the same.

For example, assuming that the image transfer frequency f of thefour-line CCD sensor 17 is 20 MHz, in order for all of the charges ofone line which are accumulated in the four-line CCD sensor to beoutputted to the exterior, a time of 8000 (CLKS)×(1/20 MHz)=400 μs isrequired. This time is the light accumulating time for one line in thesubscanning direction of the four-line CCD sensor. (In FIG. 8, imagetransfer period: t0=1/f is shown.) Hereinafter, the relationship of theanalog signal amplitude which is outputted from the four-line CCD sensor17 with a transfer CLK frequency=20 MHz and a one line lightaccumulating time tINT=400 μs, will be described. Note that thistransfer CLK frequency and one line light accumulating time of coursediffer in accordance with the specifications of the product.

The output signal amplitude of the line sensor BK, which shows whiteimage information in a case in which the monochrome document D is readat a transfer frequency of 20 MHz by using the line sensor BK, is VBK(white). The output signal amplitude VR (white) of the line sensor R,the output signal amplitude VG (white) of the line sensor G, and theoutput signal amplitude VB (white), of the line sensor B in cases inwhich a white image of the color document is read at the same transferfrequency by the line sensor R, the line sensor G, and the line sensorB, are as follows.

VBK (white)>VR (white), VBK (white)>VG (white), VBK (white)>VB (white)

In a case in which these ratios are great and the noise component whichis included in the signal is constant, the S/N ratios (the ratio of thenoise component with respect to the effective signal) of VR (white), VG(white), and VB (white) are inferior compared to VBK (white).

Here, if the spectral sensitivities of the line sensors R, G, B (seeFIG. 6) when the xenon light source having the spectral distributioncharacteristic of FIG. 7 is used are respectively 50% of the spectralsensitivity (see FIG. 5) of the line sensor BK, the following formulasare established.VBK (white)/2=VR (white), VBK (white)/2=VG (white), VBK (white)/2=VB(white)

Therefore, if the amplitudes of the output signals of the line sensorsR, G, B are double, a signal amplitude equivalent to the line sensor BKcan be obtained, and as a result, it can be thought that the S/N ratioalso is equivalent. The means for adjusting the signal amplitude of atleast one of or desirably all of the output signals of the line sensorsR, G, B to be the same as or substantially the same as the output signalamplitude of the line sensor BK, is a characterizing feature of thepresent invention.

A first embodiment of the present invention will be describedhereinafter.

The sensitivity of a CCD line sensor is defined by using the illuminancewhich is incident per unit time as shown by [V/(1x·sec)]. Therefore, thelight accumulating time of one line is changed at the time of using theline sensor BK, and at the time of using the line sensors R, G, B. Thiswill be described specifically by using FIG. 9.

The SH signal and the transfer CLK 1, 2 which are shown in FIG. 9A arethe same as the signals which are shown in FIG. 8. The SH signal is asignal which operates the shift gate at the inner portion of thefour-line CCD sensor 17, and the transfer CLK 1, 2 are signals whichcarry out the control of the analog shift register. In a case in whichimage information is read by using the line sensor BK, as describedabove, if the frequency of the transfer CLK is 20 MHz, the lightaccumulating time tINT(BK) of one line is 400 μs.

Next, in a case in which image information is read by using the linesensors R, G, B, as shown in FIG. 9B, due to the frequency of thetransfer CLK being set to 10 MHz which is ½ of the aforementionedfrequency, the light accumulating time tINT(RGB) of one line is 800 μs,which is double the above. In this way, by lowering the image transferfrequency at the time of image reading by using the line sensors R, G, Bwhose sensitivities are less than the time of reading a monochrome imageby using the line sensor BK, the amplitudes of the output signals of theline sensors R, G, B can be increased, and reading with a good S/N ratiocan be carried out.

In the above description, for explanation, it was stated that thesensitivities of the line sensors R, G, B are ½ of the sensitivity ofthe line sensor BK. However, with other ratios as well, by changing theimage frequency in accordance with the ratio, output signals from linesensors R, G, B having good S/N ratios can be provided. Further, thetransfer clock frequency may be adjusted such that the signal amplitudewhich is outputted from the line sensor BK coincides with the signalhaving the largest amplitude among the output signals of the linesensors R, G, B.

Further, in a case in which the document D is single color, it ispossible to read the document D only by the line sensor BK. At this timeas well, control which is the same as at the time of reading amonochrome document D can be carried out.

FIG. 10 is a flowchart showing the operation of the present embodiment.In a case in which a document is scanned, the CPU 100 judges whether itis reading of a color document (step S1). Namely, in a case in which thetype of the document D is set to be a monochrome document by the uservia the control panel 80, or in a case in which it is judged to be amonochrome document by an automatic sensing section 108, the CPU 100instructs the light accumulating time tINT(BK) and the transfer clockperiod t0(BK) to the CCD driver 103 (step S2), and carries out thereading operation by only the line sensor BK (step S4).

Further, in a case in which the type of the document D is set to be acolor document by the user or it is judged to be a color document by theautomatic sensing section 108, the CPU 100 instructs the lightaccumulating time tINT(RGB) and the transfer clock period t0(RGB) to theCCD driver 103 (step S3), and ignores the output signal from the linesensor BK, and carries out the reading operation by using the linesensors R, G, B (step S4).

The image signal which is provided from the four-line CCD sensor 17 issubjected to the above-described correcting processings at the imagecorrecting section 105. In a case in which a color document is read,after the CPU 100 selects the output signals from the line sensors R, G,B and stores the output signals in the RAM 102, signal processing iscarried out at the image processing section 106, and the processedsignal is provided as the image output. Further, in a case in which amonochrome document is read, after the CPU 100 selects the output signalfrom the line sensor BK and stores the output signal in the RAM 102,signal processing is carried out at the image processing section 106,and the processed signal is provided as an image output (step S5).

Next, a second embodiment of the present invention will be described.The characterizing feature of this embodiment is that the light amountcontrol of the light source is carried out in accordance with the typeof the line sensor which is used. FIG. 11 is a flowchart showing theoperation of the present embodiment. For example, when the monochromedocument D is read by the line sensor BK, the CPU 100 uses the lightsource control section 108 to lower the light amount and light the lightsource 12 (step S12). When the color document D is read by the linesensors R, G, B, the CPU 100 uses the light source control section 108to light the light source 12 at the rating (step S13). In this case, thelight amount of the light source may be controlled such that the signalamplitude outputted from the line sensor BK coincides with the signalhaving the largest amplitude among the output signals of the linesensors R, G, B.

Due to this control, the intensity of the reflected light from thedocument D can be substantially the same at the line sensor BK and atthe line sensors R, G, B when the white portion of a document is read.Further, in a case in which the light amount of the light source 12 islowered to be less than the rating and is used, there are cases in whichthe spectral distribution characteristic of the light source 12 ischanged. However, in a case in which this control is carried out, thedocument is a monochrome document. Thus, it suffices to detect only thedensity information and not the color information. Thus, even if thespectral characteristics change, no problems arise. Further, in a casein which the document D is single color, it is possible for the documentD to be read only by the line sensor BK, and at that time as well,control which is similar to the reading of a monochrome document inwhich the light amount of the light source 12 is decreased can becarried out.

Next, a third embodiment of the present invention will be described. Thestructure relating to the present embodiment is shown in FIG. 12. Inthis embodiment, as shown in FIG. 12A, the characterizing features arethat two light sources 12A, 12B are provided, and a light source whichemits light is controlled in accordance with the type of the linesensor. FIG. 13 is a flowchart showing the operation of the presentembodiment.

When the monochrome document D is read by using the line sensor BK, asshown in FIG. 12B, the CPU 100 lights the light source 12A among twolight sources, and turns off the light source 12B (step S22). Further,when the color document D is read by the line sensors R, G, B, the CPU100 carries out the control to light both of the light source 12A andthe light source 12B as shown in FIG. 12C (step S23). In this way, theintensity of the reflected light from the document can substantially thesame at the line sensor BK and at the line sensors R, G, B when the samewhite portion is read.

In this case, the CPU 100 can set the light amount of the light sourcesuch that the amplitude of the signal which is outputted from the linesensor BK when the monochrome document is read with one of the lightsources lit, coincides with the signal having the largest amplitudeamong the output signals of the line CCD sensors R, G, B when the colordocument is read with the two light sources lit.

Further, in a case in which the document D is single color, it ispossible to read the document D only by the line sensor BK. At this timeas well, control which is similar to that of monochrome documentreading, in which the document D is read with only the light source 12Alit, can be carried out. Note that there is no problem if thearrangement of the light source 12A and the light source 12B is oppositeto that in FIG. 12.

A combination of the above-described embodiments is also possible.Namely, when a monochrome document is read by the line sensor BK, theCPU 100 decreases the light amount of the light source 12 to anappropriate value. When a color document is read by the line sensors R,G, B, control can be effected to increase the light amount of the lightsource 12 as compared to the time of reading a monochrome document, orthe electric power of the light source 12 is increased to the ratedvalue, and the transfer frequency is made to be less than that at thetime of reading a monochrome document.

FIG. 14 is a view showing the processing circuit structure and thesignal waveform of an analog signal which is outputted from the CCDsensor, and FIG. 15 is a view showing the structure of a circuitrelating to a fourth embodiment.

The analog processing circuit which is outputted from the CCD sensor isgenerally, as shown in FIG. 14A, structured by a coupling capacitor 20,a CDS (Correlated Double Sampling) circuit or a sample hold circuit 21,a gain amplifier section 22, a DAC (Digital Analog Converter) 23 whichconverts a digital signal to an analog signal, an offset removingcircuit 24 for removing the DC component, and an ADC (Analog DigitalConverter) section 25. Concrete operation will be described hereinafterby using FIG. 14B.

As shown in FIG. 8 as well, the output signal is outputted from the CCDline sensor with the signal output DC voltage (Vos) as a reference. Thesignal output DC voltage (Vos) differs in accordance with the CCD linesensor. In the case of a CCD line sensor which uses a +12V power source,there is a dispersion of about 3 to 8V. For the purpose of removing theDC component of a signal having an uncertain level, the couplingcapacitor 20 is connected in series. At this time, the processing formatching the dummy pixel portion which is shown in FIG. 8 or theelectric potential of the light shield portion to the reference electricpotential (Vref) is carried out, and waveform shaping is carried out bythe CDS circuit or the sampling circuit 21, and noise is removed.

Next, processing for matching the analog signal from the CCD linesensor, from which the DC component has been removed, to the input rangeof the latter-stage ADC section 25 is carried out. At this time, DCvoltage is generated at the DAC section 23, and adjustment of the DCcomponent is carried out again at the offset removing section 24 suchthat the voltage of the light shield portion of the CCD sensor matchesthe DC voltage.

In FIG. 14B, the ‘H’ level side reference voltage, which is needed forthe converting operation of the ADC circuit, is an ADC reference(ref(+)), and the ‘L’ level side reference voltage is an ADC reference(ref(−)), and processing is carried out so as to be within this voltagerange. At this time, if a signal which is greater than the ADC reference(ref(+)) or is less than the ADC reference (ref(−)) is inputted, becausethe output of the ADC circuit is saturated, the voltage is controlled soas to absolutely not exceed the aforementioned reference.

The fourth embodiment of the present invention relates to the gainamplifier section 22 of FIG. 14A. A simple circuit example of the gainamplifier section 22 is shown in FIG. 15. The gain amplifier section isstructured by a resistor element A, a resistor element B, and anoperating amplifier OPAMP. An example of a non-inverted amplificationcircuit is shown in FIG. 15A, and an example of an invertedamplification circuit is shown in FIG. 15B.

Non-inverted amplification circuit:Vout=Vin×(1+B/A)−Vref×B/A

Inverted amplification circuit:Vout−(Vin−Vref)×B/A

As is clear from the above formulas, the amplification factor of thegain amplifier is determined by the ratio of the resistor elements A, B.

As described above, in the four-line CCD sensor 17, the sensitivities ofthe line sensor BK and the line sensors R, G, B greatly differ.Accordingly, in order to carry out the appropriate conversion at the ADCcircuit 25 which is shown in FIG. 14A, the output signal amplitudes fromthe respective line sensors are made to match.

The resistor elements of the gain amplifier section 22 which processesthe amplitude of the output signal of the line sensor BK are A(BK),B(BK), and the resistor elements of the gain amplifier section 22 whichprocesses the amplitude of the output signal of the line sensor R areA(R), B(R), and the resistor elements of the gain amplifier section 22which processes the amplitude of the output signal of the line sensor Gare A(G), B(G), and the resistor elements of the gain amplifier section22 which processes the amplitude of the output signal of the line sensorB are A(B), B(B).

In the present embodiment, the sensitivity of the line sensor BK and theratio (B(BK)/A(BK)) of the resistance values of the resistor elements,and the sensitivity of the line sensor R and the ratio (B(R)/A(R)) orthe resistor elements, and the sensitivity of the line sensor G and theratio (B(G)/A(G)) of the resistor elements, and the sensitivity of theline sensor B and the ratio (B(B)/A(B)) of the resistor elements, aremade to be appropriate.

For example, assuming that the sensitivity of the line sensor BK isR(BK), and the sensitivity R(R) of the line sensor R is R(BK)×½, thesensitivity R(G) of the line sensor G is R(BK)×⅓, and the sensitivity(B) of the line sensor B is R(BK)×¼, the respective resistor elementsare set such that the following formulas are established.B(R)/A(R)=2×B(BK)/A(BK))B(G)/A(G)=3×B(BK)/A(BK))B(B)/A(B)=4×B(BK)/A(BK))

Therefore, the resistor elements of the gain amplifier section 22 of theoutput signal of the line sensor R areA(R)=A(BK), B(R)=2×B(BK), orA(R)=(½)×A(BK), B(R)=B(BK),and the resistor elements of the gain amplifier section 22 of the outputsignal of the line sensor G areA(G)=A(BK), B(G)=3×B(BK), orA(G)=(⅓)×A(BK), B(G)=B(BK),and the resistor elements of the gain amplifier section 22 of the outputsignal of the line sensor B areA(B)=A(BK), B(B)=4×B(BK), orA(B)=(¼)×A(BK), B(B)=B(BK).

Due to the amplification factors of the gain amplifier section 22 beingset such that the above relationships are established, the output signalamplitudes from the respective line sensors can be optimized at theinput portion of the ADC section 25.

Even if the resistance values of the resistor elements A, B which aregiven in the above description are set to fixed resistances or are setto the volume resistances, because the functions are the same, there isno problem. Further, it is needless to say that, even if a resistancevalue varying means, which uses an electronic volume or the like whichis controllable from an exterior circuit of the CPU or the like, isused, the same effects can be obtained.

Next, fifth embodiment of the present invention will be described. It isdescribed above that the sensitivity of the line sensor greatly differsin accordance with whether a color filter is disposed at the receivinglight surface portion or not. As shown in FIGS. 16A and 16B, byutilizing, only at the line sensor BK at which no color filter isdisposed, a dual system output mode which outputs the accumulatedcharges separately for the odd pixels and the even pixels, reading ofsingle color documents, including monochrome documents, by using theline sensor BK can be made high-speed.

Description will be given by using, as an example, the case in FIG. 17of a 7500 pixel CCD sensor. In the CCD sensor, in the same way as thesingle system output type output signal which is shown in FIG. 8, theempty feed portion, the light shield portion, the dummy pixel portion,and the effective pixel region are provided. However, the number of thetransfer CLK which are needed for transferring all of pixels is half.

Considering the effective pixel region, in the case of FIG. 8, a numberof CLK of 7500 is needed in correspondence with the 7500 pixels.However, in the dual system output type of FIG. 16, only a number of CLKof 3750, which is half, is needed.

Therefore, the SH signal of FIG. 17 can be set at the portion which isdepicted by the broken line, and the light accumulating time for oneline can be set to be short. If the line sensor BK is used at the samelight accumulating time and at the light amount appropriate for readingby the line sensors R, G, B at which color filters are disposed at thelight receiving surface portions, the light energy which is incident onthe line sensor BK is too great, and the accumulated charges leak to theadjacent pixels. Further, depending on the incident light amount, thefear that the output is saturated arises. However, by using the dualsystem output type CCD line sensor, at the time of using the line sensorBK, the SH signal period can be set to be short, namely, the lightaccumulating time for one line can be set to be short. Accordingly, evenif the same light amount at the time of reading by the line sensors R,G, B is used for the line sensor BK, operation without the chargesleaking to the adjacent pixels as described above is possible.

Further, in the above, a CCD line sensor having a dual circuit outputmode is described. However, there are the same effects with a foursystem output as shown in FIGS. 18 and 19. Note that FIGS. 18 and 19illustrate only the line sensor BK, and the line sensors R, G, B are notillustrated. Further, the line sensors R, G, B are the single systemoutputs in the same way as in FIG. 8.

FIG. 18A shows an example in which a four system output CCD line sensoris structured by separating the line sensor BK into the odd pixels andthe even pixels, and by dividing into two an analog shift register fortransferring odd pixels (BK-ODD) and an analog shift register fortransferring even pixels (BK-EVEN).

The order of the output signals in this structure is as shown in FIG.18B. Namely, the orders of the odd pixel outputs OS-BKO1, OS-BKO2 andthe even pixel outputs OS-BKE1, OS-BKE2 are as follows.

-   -   OS-BKO1: 1, 3, 5, 7, . . . , 3745, 3747, 3749    -   OS-BKE1: 2, 4, 6, 8, . . . , 3746, 3748, 3750    -   OS-BKO2: 3751, 3753, 3755, . . . , 7495, 7497, 7499    -   OS-BKE2: 3752, 3754, 3756, . . . , 7496, 7498, 7500

FIG. 19 shows another four system output structure. This CCD line sensoris a structure which separates the odd pixels and the even pixels, andoutputs them from the both ends of the analog shift register fortransferring odd pixels (BK-ODD) and the analog shift register fortransferring even pixels (BK-EVEN). The orders of the output signals inthis structure are as in FIG. 19B. Namely, the even pixel outputsOS-BKO1, OS-BKO2, and the odd pixel outputs OS-BKE1, OS-BKE2 are asfollows.

-   -   OS-BKO1: 1, 3, 5, 7, . . . , 3745, 3747, 3749    -   OS-BKE1: 2, 4, 6, 8, . . . , 3746, 3748, 3750    -   OS-BKO2: 7499, 7497, 7495, . . . , 3755, 3753, 3751    -   OS-BKE2: 7500, 7498, 7496, . . . , 3756, 3754, 3752

The merit of the structure which is shown in FIG. 18A is that the ordersof the pixel outputs of the odd pixel output OS-BKO2 and the even pixeloutput OS-BKE2 are in time series. The demerit of the structure is that,because the pixels are outputted from the intermediate portions of theanalog shift register for transferring the odd pixels (BK-ODD) and theanalog shift register for transferring the even pixels (BK-EVEN), thereare limitations on the arrangement corresponding to the aforementionedintermediate portions of the photodiodes which are disposed on straightlines.

The merit of the embodiment of FIG. 19A is that there are no limitationson the aforementioned intermediate portions, which is described above asan example of the demerits of FIG. 18A. The demerit of the embodiment ofFIG. 19A is that, because the odd pixel output OS-BKO2 and the evenpixel output OS-BKE2 are outputted in a sequential order from the laststage of the photodiodes which are disposed on straight lines, the orderof the pixels is inverted, and a processing for reordering the pixels isindispensable.

However, both FIG. 18 and FIG. 19 are effective means for high-speeddriving the line memory BK.

In the above, the present invention is described as a scanner which isan image inputting apparatus using the four-line CCD sensor 17. However,it is needless to say that, by connecting the image inputting apparatusto an image forming apparatus, the present invention can be structuredas a copy apparatus.

FIG. 20 shows an outline view of a copy apparatus 50 which is structuredby an image inputting apparatus and an image forming apparatus. The copyapparatus 50 is connected to external computers PC1, PC2, PC3, . . . viaa network 60.

The copy apparatus 50 is formed from an image inputting apparatus 51, amemory 52 which is a recording medium, a various image processingssection 53, an image forming apparatus 54, a system control section 57which carries out control of all of these, and a control panel 58 atwhich the user carries out input directly. The image inputting apparatus51 is a scanner which reads a document image by using the four-line CCDsensor 17 as in the first to fifth embodiments which are describedabove. The image forming apparatus 54 includes a laser optical system 55using a semiconductor laser, and an image forming section 56 which formsan image with toner by using an electrophotographic process. FIG. 21shows a concrete example of the control panel 58.

FIG. 22 is a view showing the operation in a case in which the copyapparatus is used on its own. First, as shown in FIG. 22B, the user setson the image inputting apparatus 51 the document D which he/she wishesto copy, and carries out desired settings from the control panel 58which is illustrated in FIG. 21. As shown in FIG. 21, the control panel58 is structured by a document type selecting section 70, a displaysection 71 which is formed from an LCD or the like, a number of copiessetting section 72, and a start/stop section 73. The document typeselecting section 70 includes an auto color button 61 which is forsensing at the apparatus whether the document D is a monochrome documentor a color document, a full color button 62 and a black button 63 bywhich the user sets the type of the document D in advance, and acopy/scanner button 64 which sets whether the copy apparatus 50 is to beused as a copy apparatus or as a scanner which is an image inputtingapparatus. The display section 71 displays the processing contents suchas enlargement/reduction or the like, and the number of pages which wasset, and the like. The number of copies setting section 72 includes aten-key of 0 to 9 for inputting the desired number of copies and a Cbutton which is for clearing the inputted figure. The start/stop section73 includes a reset button 65 which is for initializing the conditionsset at the control panel 58, a stop button 66 which is for terminatingthe copy operation or the scanner operation in the midst of theoperation, and a start button 67 which starts the copy operation or thescanner operation. This structure of the control panel 58 is an example,and for example, there are structures in which various setting buttonsof the control panel are set in a display section which is structured bya touch panel using a liquid crystal.

As shown in FIG. 22B, when the document D is set, the cover 11 fordocument fixing is closed, and the type of the document, the page size,the number of copies to be formed for a document of one page, and thelike are set by using the control panel 58. By pressing the start button67, the copy operation starts. At this time, the image information whichis read at the image inputting apparatus 51 is temporarily accumulatedin the memory 52 which is a recording medium. The memory 52 isstructured by a page memory having a larger capacity than a capacitywhich can store all of the image information of the largest size whichcan be copied. The image information which is outputted from the memory52 is, at the various image processings section 53 of the subsequentstage, subjected to enlargement or equivalent magnification or reductionprocessing, and the RGB image information is converted to Y (yellow), M(magenta), C (cyan), K (black) signals for color reproduction by usingtoners, and is subjected to gradation correction and the like, and isconverted into control signals of semiconductor lasers which areinputted to a laser optical system 55 at the subsequent stage. The imagesignals become the light output of the semiconductor lasers at the laseroptical system 55, and the semiconductor lasers are irradiated onto aphotosensitive body (not shown) of the image forming section 56. Theimage forming section 56 forms an image by an electrophotographicprocess.

At this time, in a case in which the type of the document D is set to bea monochrome document by the user or it is judged to be a monochromedocument by automatic sensing, the reading operation is carried out byonly the line sensor BK. Further, in a case in which the type of thedocument D is set to be a color document by the user or is judged to bea color document by automatic sensing, the output signal from the linesensor BK is ignored, and the reading operation by using the linesensors R, G, B is carried out.

FIG. 23 shows an example of operation as a network printer which printsimage information from an external computer by the network connectionvia the system control section 57. At the time of this operation, theimage information which is outputted from an external computer, forexample, the PC1, is stored in the memory 52 via the system controlsection 57. Thereafter, in the same way as in the copy operation, theimage is printed onto a paper at the image forming section 54 via thevarious image processings section 53, and is outputted.

FIG. 24 shows an example of operation as a network scanner which outputsthe image information, which is read by using the image inputtingapparatus 51, to the computer by network connection via the systemcontrol section 57.

As shown in FIG. 24B, the user sets the document D at the scanner whichis the image inputting apparatus 51, and sets the type of the documentD, the size of the document D, the reading resolution, and scanneroperation at the control panel 58. Further, the address of the computerPC1, which is connected to the network and is the sending destination ofthe image information, is set, and by pressing the start button, theoperation starts. The image information which is read at the imageinputting apparatus 51 is stored in the memory 52, and thereafter, adesired compression processing such as JPEG or PDF format is carried outat the various image processings section 53 which is the subsequentstage. The compressed image information is transferred to the externalcomputer PC1 through the network 60 via the system control section 57.

At this time, in a case in which the type of the document D is set to bea monochrome document by the user or judged to be a monochrome documentby automatic sensing, the reading operation is carried out by only theline sensor BK. Further, in a case in which the type of the document Dis set to be a color document by the user or is judged to be a colordocument by automatic sensing, the output signal from the line sensor BKis ignored, and reading operation by using the line sensors R, G, B iscarried out.

Further, whether the image information is image information which isread by only the line sensor BK or is image information which is read byusing the line sensors R, G, B can be simultaneously attached andtransferred to the external computer PC1.

As described above, in accordance with the present invention, in a casein which a document is read by using a four-line CCD sensor, which isstructured by a three-line CCD sensor for reading a color document inwhich color filters are disposed on the surfaces of the light receivingelement and a CCD sensor at which no color filter is disposed, in thecase of a monochrome document or a single color document, the documentcan be read at high speed, and in the case of a color document, readingwith high gradation reproducibility can be carried out.

Further, conventionally, when a monochrome document is read by using acolor scanner having the three-line CCD sensor which is described above,at the portions at which the image information changes from white toblack or from black to white, there is a so-called coloring phenomenonin which a false color is generated due to the difference in thephysical positions of the respective line sensors. However, by using acolor scanner having the four-line CCD sensor of the present invention,the above-described coloring phenomenon does not arise.

Further, in accordance with the present invention, by setting two ormore output systems of the CCD line sensor at which no color filter isdisposed, it is possible to read an image at high speed by using thesame light source as at the time of carrying out the reading operationusing the three-line CCD sensor in which the color filters are disposed.

1. An image inputting apparatus which reads a document optically andprovides image information which corresponds to a document image, theimage inputting apparatus comprising: a light source which irradiateslight onto the document; a four-line CCD sensor which includes a firstCCD line sensor which is structured by a three-line CCD sensor in whichcolor filters are respectively disposed on surfaces of light receivingelements, and a second CCD line sensor which is structured by a one-lineCCD sensor in which no color filter is disposed, the four-line CCDsensor receiving reflected light from the document and providing animage signal which corresponds to the reflected light; a driving sectionwhich supplies a signal including an image transfer clock to thefour-line CCD sensor, and drives the four-line CCD sensor; adjustingsection which adjusts an amplitude of at least one signal among signalsoutputted from the first CCD line sensor when a color document is readand an amplitude of a signal which is outputted from the second CCD linesensor when a monochrome document is read, to be substantially equal toone another; and a selecting section which selectively provides outputof the first CCD line sensor in a case in which a color document isread, and selectively provides output of the second CCD line sensor in acase in which a monochrome document is read.
 2. An apparatus accordingto claim 1, wherein the adjusting section adjusts one signal amplitudeamong signals which are outputted from the first CCD line sensor, and anamplitude of a signal which is outputted from the second CCD line sensorwhen a single color document is read, to be substantially equal to oneanother, and the selecting section selectively provides the output ofthe second CCD line sensor in a case in which the single color documentis read.
 3. An apparatus according to claim 1, wherein, at a time ofreading a color document and at a time of reading a monochrome document,the adjusting section changes a one scan line reading time of a documentby changing a frequency of the image transfer clock which is suppliedfrom the driving section to the four-line CCD sensor.
 4. An apparatusaccording to claim 3, wherein the adjusting section sets an imagetransfer frequency at a time of reading a color document to be lowerthan that at a time of reading a monochrome document.
 5. An apparatusaccording to claim 1, wherein the adjusting section includes a lightamount changing section which changes a light amount of the light sourceat a time of reading a color document and at a time of reading amonochrome document.
 6. An apparatus according to claim 5, wherein thelight amount changing section sets the light amount at the time ofreading a color document to be greater than that at the time of readinga monochrome document.
 7. An apparatus according to claim 5, wherein thelight amount changing section controls the light amount of the lightsource such that an amplitude of a signal which is outputted from thesecond CCD line sensor coincides with an amplitude of a signal whoseamplitude is largest among output signals of a three-line CCD sensorwhich forms the first CCD line sensor.
 8. An apparatus according toclaim 1, wherein a plurality of light sources are provided, and theadjusting section turns on the plurality of light sources at a time ofreading a color document, and turns on one light source among theplurality of light sources at a time of reading a monochrome document.9. An apparatus according to claim 8, wherein the adjusting section setsa light amount of the light source such that an amplitude of a signalwhich is outputted from the second CCD line sensor when a monochromedocument is read by turning on one of the plurality of light sourcescoincides with an amplitude of a signal whose amplitude is largest amongoutput signals of a three-line CCD sensor which forms the first CCD linesensor.
 10. An apparatus according to claim 1, wherein the adjustingsection includes first to third amplifiers which amplify, at first tothird amplification factors respectively, output signals of thethree-line CCD line sensor which forms the first CCD line sensor, and afourth amplifier which amplifies an output signal of the second CCD linesensor at a fourth amplification factor which is less than the first tothird amplification factors.
 11. An apparatus according to claim 10,wherein the adjusting section controls the amplification factors of thefirst to fourth amplifiers such that amplitudes of the output signals ofthe three-line CCD sensor which forms the first CCD line sensor and asignal amplitude which is outputted from the second CCD line sensor allcoincide.
 12. An apparatus according to claim 1, wherein outputs of aplurality of light receiving elements which form the second CCD linesensor are divided into a plurality of groups, and respective groupsoutput serial image signals simultaneously.
 13. An apparatus accordingto claim 1, wherein outputs of a plurality of light receiving elementswhich form the second CCD line sensor are divided into a plurality ofgroups, and respective groups output serial image signalssimultaneously, and wherein light amounts of the light source are thesame at a time of reading a color document and at a time of reading amonochrome document.
 14. An apparatus according to claim 1, furthercomprising: a user interface which is for a user to designate whether adocument is a color document, a monochrome document or a single colordocument, wherein in a case in which the document is designated to be acolor document by the user interface, the selecting section selects andprovides output of a three-line CCD sensor which forms the first CCDline sensor, and in a case in which the document is designated to be oneof a monochrome document and a single color document, the selectingsection selects and provides output of the second CCD line sensor. 15.An apparatus according to claim 1, further comprising: a documentautomatic sensing section which senses whether a document is a colordocument, a monochrome document or a single color document, wherein in acase in which the document is detected to be a color document by thedocument automatic sensing section, the selecting section selects andprovides output of a three-line CCD sensor which forms the first CCDline sensor, and in a case in which the document is detected to be oneof a monochrome document and a single color document, the selectingsection selects and provides output of the CCD line sensor in which nocolor filter is disposed.
 16. An apparatus according to claim 1, whereinthe image inputting apparatus is connected to a network and is used as anetwork scanner, and when the image inputting apparatus transmits imageinformation to a computer which is connected via the network, the imageinputting apparatus simultaneously transmits an identification signalwhich expresses whether an image is a color image which is read by usingthe color filters or a monochrome image which is read without using acolor filter.
 17. An image forming apparatus which reads a documentoptically and forms an image which corresponds to a document image, theimage forming apparatus comprising: a light source which irradiateslight onto the document; a four-line CCD sensor which includes a firstCCD line sensor which is structured by a three-line CCD sensor in whichcolor filters are respectively disposed on surfaces of light receivingelements, and a second CCD line sensor which is structured by a one-lineCCD sensor in which no color filter is disposed, the four-line CCDsensor receiving reflected light from the document and providing animage signal which corresponds to the reflected light; a driving sectionwhich supplies a signal including an image transfer clock to thefour-line CCD sensor, and drives the four-line CCD sensor; adjustingsection for adjusting an amplitude of at least one signal among signalswhich are outputted from the first CCD line sensor at a time of readinga color document, and an amplitude of a signal which is outputted fromthe second CCD line sensor at a time of reading a monochrome document,to be substantially equal to one another; a selecting section whichselectively provides output of the first CCD line sensor in a case inwhich a color document is read, and selectively provides output of thesecond CCD line sensor in a case in which a monochrome document is read;and an image forming section which forms an image on a medium on whichan image is to be formed, on the basis of image signals which areselectively provided from the selecting section.
 18. An apparatusaccording to claim 17, wherein the adjusting section changes a one scanline reading time of a document by changing a frequency of the imagetransfer clock which is supplied from the driving section to thefour-line CCD sensor, at a time of reading a color document and at atime of reading a monochrome document.
 19. An apparatus according toclaim 17, wherein the adjusting section includes a light amount changingsection which changes a light amount of the light source at the time ofreading a color document and at the time of reading a monochromedocument.
 20. An image inputting method which reads a document opticallyand provides image data which corresponds to a document image, the imageinputting method comprising the steps of: irradiating light onto thedocument; supplying a signal including an image transfer clock to afour-line CCD sensor, and driving the four-line CCD sensor, wherein thefour-line CCD sensor includes a first CCD line sensor which isstructured by a three-line CCD sensor in which color filters arerespectively disposed on surfaces of light receiving elements and asecond CCD line sensor which is structured by a one-line CCD sensor inwhich no color filter is disposed, and receiving reflected light fromthe document, and providing an image signal which corresponds to thereflected light; adjusting an amplitude of at least one signal amongsignals which are outputted from the first CCD line sensor at a time ofreading a color document and an amplitude of a signal which is outputtedfrom the second CCD line sensor at a time of reading a monochromedocument, to be substantially equal to one another; and selectivelyproviding output of the first CCD line sensor in a case in which a colordocument is read, and selectively providing output of the second CCDline sensor in a case in which a monochrome document is read.
 21. Animage inputting apparatus which reads a document optically and providesimage information which corresponds to a document image, the imageinputting apparatus comprising: a light source which irradiates lightonto the document; a four-line sensor which includes a first line sensorwhich is structured by a three-line sensor in which color filters arerespectively disposed on surfaces of light receiving elements, and asecond line sensor which is structured by a one-line sensor in which nocolor filter is disposed, the four-line sensor receiving reflected lightfrom the document and providing an image signal which corresponds to thereflected light; a driving section which supplies a signal including animage transfer clock to the four-line sensor, and drives the four-linesensor; an adjusting section which adjusts an amplitude of at least onesignal among signals outputted from the first line sensor when a colordocument is read and an amplitude of a signal which is outputted fromthe second line sensor when a monochrome document is read, to besubstantially equal to one another; and a selecting section whichselectively provides output of the first line sensor in a case in whicha color document is read, and selectively provides output of the secondline sensor in a case in which a monochrome document is read.
 22. Anapparatus according to claim 21, wherein the adjusting section adjustsone signal amplitude among signals which are outputted from the firstline sensor, and an amplitude of a signal which is outputted from thesecond line sensor when a single color document is read, to besubstantially equal to one another, and the selecting sectionselectively provides the output of the second line sensor in a case inwhich the single color document is read.
 23. An apparatus according toclaim 21, wherein, at a time of reading a color document and at a timeof reading a monochrome document, the adjusting section changes a onescan line reading time of a document by changing a frequency of theimage transfer clock which is supplied from the driving section to thefour-line sensor.
 24. An apparatus according to claim 23, wherein theadjusting section sets an image transfer frequency at a time of readinga color document to be lower than that at a time of reading a monochromedocument.
 25. An apparatus according to claim 21, wherein the adjustingsection includes a light amount changing section which changes a lightamount of the light source at a time of reading a color document and ata time of reading a monochrome document.
 26. An apparatus according toclaim 25, wherein the light amount changing section sets the lightamount at the time of reading a color document to be greater than thatat the time of reading a monochrome document.
 27. An apparatus accordingto claim 25, wherein the light amount changing section controls thelight amount of the light source such that an amplitude of a signalwhich is outputted from the second line sensor coincides with anamplitude of a signal whose amplitude is largest among output signals ofa three-line sensor which forms the first line sensor.
 28. An apparatusaccording to claim 21, wherein a plurality of light sources areprovided, and the adjusting section turns on the plurality of lightsources at a time of reading a color document, and turns on one lightsource among the plurality of light sources at a time of reading amonochrome document.
 29. An apparatus according to claim 28, wherein theadjusting section sets a light amount of the light source such that anamplitude of a signal which is outputted from the second line sensorwhen a monochrome document is read by turning on one of the plurality oflight sources coincides with an amplitude of a signal whose amplitude islargest among output signals of a three-line sensor which forms thefirst line sensor.
 30. An apparatus according to claim 21, wherein theadjusting section includes first to third amplifiers which amplify, atfirst to third amplification factors respectively, output signals of thethree-line line sensor which forms the first line sensor, and a fourthamplifier which amplifies an output signal of the second line sensor ata fourth amplification factor which is less than the first to thirdamplification factors.
 31. An apparatus according to claim 30, whereinthe adjusting section controls the amplification factors of the first tofourth amplifiers such that amplitudes of the output signals of thethree-line sensor which forms the first line sensor and a signalamplitude which is outputted from the second line sensor all coincide.32. An apparatus according to claim 21, wherein outputs of a pluralityof light receiving elements which form the second line sensor aredivided into a plurality of groups, and respective groups output serialimage signals simultaneously.
 33. An apparatus according to claim 21,wherein outputs of a plurality of light receiving elements which formthe second line sensor are divided into a plurality of groups, andrespective groups output serial image signals simultaneously, andwherein light amounts of the light source are the same at a time ofreading a color document and at a time of reading a monochrome document.34. An apparatus according to claim 21, further comprising: a userinterface which is for a user to designate whether a document is a colordocument, a monochrome document or a single color document, wherein in acase in which the document is designated to be a color document by theuser interface, the selecting section selects and provides output of athree-line sensor which forms the first line sensor, and in a case inwhich the document is designated to be one of a monochrome document anda single color document, the selecting section selects and providesoutput of the second line sensor.
 35. An apparatus according to claim21, further comprising: a document automatic sensing section whichsenses whether a document is a color document, a monochrome document ora single color document, wherein in a case in which the document isdetected to be a color document by the document automatic sensingsection, the selecting section selects and provides output of athree-line sensor which forms the first line sensor, and in a case inwhich the document is detected to be one of a monochrome document and asingle color document, the selecting section selects and provides outputof the line sensor in which no color filter is disposed.
 36. Anapparatus according to claim 21, wherein the image inputting apparatusis connected to a network and is used as a network scanner, and when theimage inputting apparatus transmits image information to a computerwhich is connected via the network, the image inputting apparatussimultaneously transmits an identification signal which expresseswhether an image is a color image which is read by using the colorfilters or a monochrome image which is read without using a colorfilter.
 37. An image forming apparatus which reads a document opticallyand forms an image which corresponds to a document image, the imageforming apparatus comprising: a light source which irradiates light ontothe document; a four-line sensor which includes a first line sensorwhich is structured by a three-line sensor in which color filters arerespectively disposed on surfaces of light receiving elements, and asecond line sensor which is structured by a one-line sensor in which nocolor filter is disposed, the four-line sensor receiving reflected lightfrom the document and providing an image signal which corresponds to thereflected light; a driving section which supplies a signal including animage transfer clock to the four-line sensor, and drives the four-linesensor; an adjusting section for adjusting an amplitude of at least onesignal among signals which are outputted from the first line sensor at atime of reading a color document, and an amplitude of a signal which isoutputted from the second line sensor at a time of reading a monochromedocument, to be substantially equal to one another; a selecting sectionwhich selectively provides output of the first line sensor in a case inwhich a color document is read, and selectively provides output of thesecond line sensor in a case in which a monochrome document is read; andan image forming section which forms an image on a medium on which animage is to be formed, on the basis of image signals which areselectively provided from the selecting section.
 38. An apparatusaccording to claim 37, wherein the adjusting section changes a one scanline reading time of a document by changing a frequency of the imagetransfer clock which is supplied from the driving section to thefour-line sensor, at a time of reading a color document and at a time ofreading a monochrome document.
 39. An apparatus according to claim 37,wherein the adjusting section includes a light amount changing sectionwhich changes a light amount of the light source at the time of readinga color document and at the time of reading a monochrome document. 40.An image inputting method which reads a document optically and providesimage data which corresponds to a document image, the image inputtingmethod comprising the steps of: irradiating light onto the document;supplying a signal including an image transfer clock to a four-linesensor, and driving the four-line sensor, wherein the four-line sensorincludes a first line sensor which is structured by a three-line sensorin which color filters are respectively disposed on surfaces of lightreceiving elements and a second line sensor which is structured by aone-line sensor in which no color filter is disposed, and receivingreflected light from the document, and providing an image signal whichcorresponds to the reflected light; adjusting an amplitude of at leastone signal among signals which are outputted from the first line sensorat a time of reading a color document and an amplitude of a signal whichis outputted from the second line sensor at a time of reading amonochrome document, to be substantially equal to one another; andselectively providing output of the first line sensor in a case in whicha color document is read, and selectively providing output of the secondline sensor in a case in which a monochrome document is read.
 41. Animage inputting apparatus, comprising: a light source which irradiateslight onto a document; a four-line sensor which includes a first linesensor which is structured by a three-line sensor in which color filtersare respectively disposed on surfaces of light receiving elements, and asecond line sensor which is structured by a one-line sensor, thefour-line sensor receiving reflected light from the document andproviding an image signal which corresponds to the reflected light; adriving section which supplies a signal including image transfer clockto the four-line sensor, and drives the four-line sensor; and anadjusting section which adjusts an amplitude of at least one signalamong signals outputted from the first line sensor when a color documentis read and an amplitude of a signal which is outputted from the secondline sensor when a monochrome document is read, to be substantiallyequal to one another.
 42. An image forming apparatus, comprising: alight source which irradiates light onto a document; a four-line sensorwhich includes a first line sensor which is structured by a three-linesensor in which color filters are respectively disposed on surfaces oflight receiving elements, and a second line sensor which is structuredby a one-line sensor, the four-line sensor receiving reflected lightfrom the document and providing an image signal which corresponds to thereflected light; a driving section which supplies a signal including animage transfer clock to the four-line sensor, and drives the four-linesensor; an adjusting section for adjusting an amplitude of at least onesignal among signals which are outputted from the first line sensor whena multiple color document is read and an amplitude of a signal which isoutputted from the second line sensor when a single color or monochromedocument is read, to be substantially equal to one another; and aselecting section which selectively provides the output of the firstline sensor or the output of the second line sensor.